Question: Which of these numbers is composite? ${29,\ 31,\ 57,\ 61,\ 67}$
Explanation: A composite number is a number that has more than two factors (including 1 and itself). 29, 31, 61, and 67 each have only two factors. The factors of 57 are 1, 3, 19, and 57. Thus, 57 is the composite number.